Induction of human HL-60 leukemic cell differentiation by immune interferon is accompanied by an increase in NADase activity and by a decrease in DNA-binding proteins.

The effects of highly purified human immune interferon (IFN-gamma) on the differentiation of human promyelocytic HL-60 leukemic cells have been studied. The addition of 100 units/ml interferon to HL-60 cells for 5 days results in morphological changes characteristic of macrophages. At the biochemical level, there is a 3-fold increase in the specific activity of the enzyme NADase. Kinetic analysis shows that IFN-gamma causes an increase in the Vmax of NADase without affecting the apparent Km. Pulse labeling experiments with [35S] methionine show a marked change in the de novo synthesis of several proteins in the course of interferon treatment. Chromatography on DNA-agarose show that after treatment with interferon for 24 or 48 h, there is a 60-70% decrease in newly synthesized proteins which bind DNA-agarose and can be subsequently displaced from the column with 2% SDS containing buffer (from 7.7-8.7% bound in control cell extracts to 2.6-3.1% bound in interferon treated cell extract).

Protein pyrolysate products.

Diet and nutrition may be responsible for 60% of the total cancer incidence for women and greater than 40% for men. Fat, animal protein, and meat consumption are highly correlated with colon cancer incidence. The charcoal broiling of meat and fish yield mutagenic substances. Many findings support the hypothesis that the predominant mutagens are formed by the Maillard reaction. A number of mutagenic compounds have been identified both from cooked foods and from protein pyrolysates. The identified compounds are N-heterocyclic primary amine derivatives of either carbolines, imidazoquinolines, or imidazoquinoxalines. The carboline-type mutagens are structurally related to the known carcinogens 2-acetylaminofluorene (AAF) and 2-aminofluorene (AF), while the imidazoquinoline and imidazoquinoxaline types are believed to resemble 3,2'-dimethyl-4-aminobiphenyl (DMAB). Studies support the theory that these compounds require metabolic activation and are carcinogenic. The major metabolites of several compounds have been identified as the N-hydroxy derivatives. DNA binding was found to be a necessary but not a sufficient condition for mutagenesis. The modified base products have been identified as C-8-guanyl derivatives, resembling adducts formed by the carcinogenic aromatic amines.

Formation of mutagens in cooked foods. V. The mutagen reducing effect of soy protein concentrates and antioxidants during frying of beef.

Cooking beef patties results in the formation of mutagens detectable by Salmonella typhimurium TA98 with metabolic activation. Decreased mutagenic activity results when frying beef with added soy protein concentrates (SPC). The reduction in mutagenicity takes place during the cooking process. Whereas fried beef hamburgers show high mutagenic activity, by comparison, similarly fried soy-hamburgers have much less mutagenic activity. Volumetric effects are responsible partly for the reduction on mutagenicity by SPC. Naturally occurring antioxidants in SPC, such as chlorogenic acid, also play a role. Also, a commonly used antioxidant, butylated hydroxyanisole (BHA), has been found effective in reducing the mutagenicity of fried beef. Thus, the addition of SPC or BHA in beef patties may provide a practical way of reducing mutagen formation during frying of beef.

Formation of mutagens in cooked foods. IV. Effect of fat content in fried beef patties.

Cooking beef patties results in the formation of mutagens detectable by Salmonella typhimurium TA98 with metabolic activation. We now show that the amount of fat in beef affects the quantity of mutagens formed. While char increases with increasing fat, over the range of 5-309% of added fat content, mutagenicity reaches a peak at 10% added fat and subsequently decreases. Thus, char formation is not an accurate measure of mutagenicity. These results suggest that fat plays an important role in mutagen formation in fried beef.

Formation of mutagens in cooked foods. III. Isolation of a potent mutagen from beef.

The major mutagenic component of fried beef has been isolated using a series of chromatographic steps. The pure compound has been analyzed by low and high resolution mass spectroscopy and nuclear magnetic resonance spectroscopy. The results indicate that the molecular weight of this extremely mutagenic compound is 198, with an elemental composition of C11H10N4. The compound is different from the known mutagenic pyrolysis products of amino acids or proteins.